Gretel G. Pellegrini

Salivary bone turnover markers in healthy pre- and postmenopausal women: daily and seasonal rhythm

No studies had investigated circadian and circannual rhythms of bone biomarkers in whole saliva. We evaluated the salivary daily and seasonal rhythm of carboxy-terminal telopeptide of type I collagen (CTX) and bone alkaline phosphatase (b-ALP). Forty clinical and oral healthy ambulatory pre- and postmenopausal women from two southern Argentine cities: Comodoro Rivadavia (latitude 45º S) and Ushuaia (latitude 54º S) were included in the study. CTX levels were evaluated in serum, urine, and saliva, and b-ALP levels were measured in serum and saliva. In both groups of women, salivary CTX showed a maximum percentage of change early in the morning (80%) and a minimum in the late afternoon (45%), similarly to the pattern observed in urinary samples. No daily rhythm was observed in serum or salivary b-ALP. 25-Hydroxyvitamin D levels decreased in winter vs. summer (p < 0.01) without differences between the two studied groups. Conversely, parathormone reached higher levels in winter (p < 0.05) which induced a slight non-significant increment in salivary CTX and b-ALP levels. The results showed that, as in serum and urinary samples, salivary CTX exhibits daily and a slight seasonal rhythmicity. Whole non-stimulated saliva is a useful tool to detect several oral and systemic diseases because it has important advantages compared to serum and urinary samples. Then, it may also be a promising sample to test changes in bone metabolism contributing to diagnose and to monitor the therapy of several metabolic bone diseases.

Daily rhythm in bone resorption in humans: preliminary observations on the effect of hypoparathyroidism or blindness

Abstract While 24-hour rhythmicity of bone formation is largely dependent on serum cortisol, the physiological basis for daily changes in bone resorption remains uncertain. The present study was carried out to assess the effect of a chronic lack of PTH or blindness on overall daily bone resorption in a small group of human subjects. Three groups of subjects were examined: (a) hypoparathyroid (n = 6, 4 female); (b) congenitally blind (n = 6, 2 female); (c) control (n = 6, 6 female). All individuals were admitted to the hospital at 0600 h and stayed there for 26 h with normal day/night activity. Urine samples were obtained every 4 h, starting at 0800 h. Urinary cross-linked N-telopeptide of type I collagen (NTX) was measured by ELISA and expressed as the ratio with urinary creatinine levels. Mean 24-h concentration of urinary NTX was lower in hypoparathyroid and blind subjects as compared to controls (p < 0.001). Significant 24-h profiles of urinary NTX/creatinine concentration (expressed as % of change of the mean 24 h level) were observed in the three groups. While control and hypoparathyroid individuals showed maximal levels at early morning and a minimum at late afternoon (2000 h), blind subjects exhibited a minimum at early afternoon (1600 h). The results suggest that neither the lack of PTH nor the lack of vision suppress the circadian rhythmicity of urinary NTX in humans. Further studies comprising larger amounts of subjects are needed to support this conclusion.

BONE MASS RECOVERY OF OSTEOPENIC VITAMIN D INSUFFICIENT RATS FROM STRONTIUM RANELATE TREATMENT: DOES THE RESPONSE DEPEND ON VITAMIN D NUTRITIONAL STATUS OR ON SOURCE OF VITAMIN D (D2 VERSUS D3)?

It was investigated if Vitamin D (Vit D) status or source (Vitamin D2 vs. Vitamin D3) interferes with bone mass recovery from strontium ranelate (SrRa) treatment of rats with Vit D insufficiency and established osteopenia. Osteopenic and Vit D insufficient rats were divided in groups to complete a 105-day period. First experiment: The rats were fed with diets that only varied in Vit D (100 vs. 0 IU%) and/or SrRa (0 vs. 900 mg/kg/day) content. A SHAM group received Vit D throughout the experience. Second experiment: Rats were divided into groups and received Vit D2 or Vit D3 through diet and SrRa by gavages in a fasting state. Two SHAM groups received Vit D2 or Vit D3 throughout the study. Results: Levels of 25-hydroxyvitamin 25OHD were reduced in groups lacking dietary Vit D (p < 0.001). Independently of Vit D status or source, SrRa did not affect body weight gain or bone alkaline phosphatase levels; osteocalcin and C-terminal telopeptide of type I collagen levels were reduced (p < 0.05) and bone Sr content was increased (p < 0.0001). Although no improvement in biomechanical parameters was observed, total skeletal bone mineral content and proximal tibial bone mineral density were increased (p < 0.05). There was a reduction in the trabecular number and an increase in the trabecular surface and bone volume without reaching SHAM levels. Conclusion: This is the first study that examined SrRa effects in an osteopenic vitamin D–insufficient experimental model. Under our experimental conditions, SrRa increased bone Sr content independently of Vit D status or source; however, no evidence of an anabolic or antifracture effect was found, and only a slight decrease in some bone resorption parameters was observed.